Managing forests for watershed protection in Taiwan

Few places in the world experience the severity of watershed management problems faced by Taiwan. The island is 74% mountainous with steep slopes and weak geologic formations. Each typhoon season brings torrential rainfall, resulting in frequent flooding, debris torrents, and landslides. On the other hand, seasonal water shortages occur in parts of the island, a problem that will become more severe as Taiwan's population expands from its current 590 people per square kilometer. Despite forest exploitation earlier in this century, Taiwan now manages its 58% forest cover primarily for watershed protection with an emphasis on slope stabilization. Watershed protection in the past has relied heavily on engineering structures on hillslopes and along stream channels, which raises some concern about unwanted downstream effects. Forest clearing for crops, road construction and various development schemes are also of concern because of reduced slope stability, increased sediment and pollutant delivery downstream, and increased peak flows. This paper discusses watershed management needs for the coming century, considering cumulative effects of past land use changes on Taiwan's mountainous watersheds, and the issue of non-structural versus structural engineering solutions to watershed problems. Watershed management implications of institutional and policy changes related to forest lands administration are also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.